The present invention is related to passenger detection systems, and in particular to passenger detection systems that can readily classify an attribute of a passenger of an automobile in which an air bag device is installed.
Air bag devices ease the shock that a passenger experiences during an automobile collision. Air bags are installed in front of the driver's and passenger's seats. Air bags may be installed in other locations, such as to the side of a forward facing passenger.
In a typical air-bag system, the control system includes a control circuit that receives a signal from an electrical acceleration sensor (shock detection sensor), and transmits control signals to the gates of normally-open semiconductor switching elements. The switching elements are respectively connected in parallel paths between a system operating voltage and ground. Each path includes a safing sensor, a squib circuit and the switching element. The squib circuits are connected to the gas sources of the air bag devices.
In operation, the air bag control system only deploys the air bags when both of the safing sensors close, and when the electrical acceleration sensor closes. Current flows from the system operating voltage to ground through each of the squib circuits, thereby causing respective gas sources to deploy (inflate) the air bags.
Many air bags are designed to deploy in front of the torso of an adult passenger seated in the seat. When a rear facing infant seat (hereafter RFIS) is located on the front passenger seat, it is desirable for the passenger-side air bag not to deploy. It may also be desirable for the passenger-side air bag not to deploy for a forward facing child seat (hereafter “FFCS”) or child. Likewise, deployment may be limited for side impact airbags based on whether a child or short person is leaning towards the air bag.
Passenger detection sensor types have been proposed for detecting a RFCS, an FFCS or children. Systems using electric fields to detect characteristics of a load in a seat are disclosed in U.S. Pat. Nos. 5,948,031, 6,329,913 and 6,329,914. Other systems using capacitive sensing, such as systems to detect a change in phase or frequency due to the presence of a passenger, have also been proposed. Both types of systems rely on transmission and reception from one or more antenna or electrodes.
Since airbags deploy forcefully and quickly, sensors for correctly determining whether any passenger is in a desirable or undesirable location are desired. Such sensors may prevent injury. By correctly avoiding deployment of the airbag when no passenger is present, replacement costs may be avoided.